窄带隙IV-VI族半导体PbTe(111)的表面氧化及氧的热脱附机理

Oxidation and Oxygen Thermal Desorption Mechanism on Narrow-Gap IV-VI Semiconductor PbTe(111)Surface

利用X射线光电子能谱(XPS)、扫描隧道显微镜(STM)以及低能电子衍射(LEED),对PbTe(111)薄膜的表面氧化及氧的热脱附机理进行了研究.结果表明:PbTe(111)薄膜经500VAr+轰击加上250℃高温退火循环处理,可得到呈(1×1)周期性排列的清洁表面.将此清洁表面暴露于大气两天后,表面被氧化形成了PbO2、PbO和TeO2,氧化层的厚度大于2个单原子层(ML),与清洁PbTe(111)表面相比,被氧化的PbTe(111)表面的Te3d5/2与Pb4f7/2芯态谱峰的面积比明显减小,表明被氧化的PbTe(111)表面是富Pb的.在热脱附处理过程中,PbO2和TeO2的芯态峰消失,且O1s芯态峰的强度迅速减弱,表明加热处理不仅使PbO2和TeO2发生了分解,同时也使氧发生了脱附,但PbO即使在350℃退火仍吸附于PbTe(111)表面.

Oxidation and thermal desorption mechanism on the PbTe（111）surface were investigated using X-ray photoemission spectroscopy（XPS）,scanning tunneling microscopy（STM）,and low-energy-electron diffraction（LEED）.The initial cleaning of the surface by 500 V Ar ＋ sputtering followed by annealing at 250℃ yielded a perfect（1×1）PbTe（111）surface.XPS measurements showed that PbO 2,PbO,and TeO 2 were present at the PbTe（111）surface after air exposure for 2 days,and the intensity ratio of Te 3d 5/2 and Pb 4f 7/2 increased rapidly compared to that of the clean PbTe（111）surface,indicating Te depletion and Pb enrichment of the surface.XPS and STM measurements showed that the thickness of the oxide layer was more than 2 monolayers（MLs）.During thermal treatment,the core levels of PbO 2 and TeO 2 disappeared and the intensity of the O 1s core level decreased,indicating surface decomposition of PbO 2 and TeO 2,and desorption of oxygen,whereas PbO was still present on the surface after annealing at up to 350℃.